Method for controlling a drive device in a vehicle during starting process and corresponding control system

ABSTRACT

In a method for controlling a drive device in a motorized vehicle during driving off, a driving off process which is to be carried out at a particular time is detected based on sensed operational and driving states of the vehicle. In order to support the driver during the driving off process, the engine setpoint rotational speed is increased automatically and independently of the driver to a value which exceeds the idling setpoint rotational speed of the engine. The engine actual rotational speed is adjusted to the setpoint rotational speed by means of a rotational speed controller by additional injection of fuel.

This application claims the priority of German patent document 101 55216.5, filed 09 Nov. 2001 (PCT International Application No.PCT/EP02/10503, filed 19 Sep. 2002) the disclosure of which is expresslyincorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a method and apparatus for controlling a drivedevice in a vehicle during driving off processes, in which the vehiclecommences movement.

German patent document DE 41 18 332 A1 discloses a system forcontrolling a drive device of a vehicle, which is configured for drivingin low speed stop-and-go situations in which the vehicle repeatedlystarts and stops. The driving force of the vehicle is controlledautomatically, and the vehicle is automatically accelerated from astationary state to a target speed, independently of actuation of theaccelerator pedal by the driver (provided that the brake pedal is notactivated). As soon as the brake pedal is depressed, the automaticacceleration process is aborted and the vehicle is braked again to thestationary state. As soon as the driver stops activating the brake pedalagain, the vehicle is accelerated once more to the target speed.

The application of this known control device is restricted to thestop-and-go mode. However, this document does not provide any indicationof how to optimize the driving off processes in the normal operationalstate of the vehicle, in order to reduce the fuel consumption andemissions of pollutants.

German patent document DE 196 16 960 A1 discloses a device forautomatically setting a clutch in the drive train of a motor vehiclewith an internal combustion engine, during driving off processes and/orgear changing processes. The device comprises an engine rotational speedcontrol circuit which, during driving off and/or gear changing, adjuststhe engine rotational speed to a setpoint value which is dependent onthe position of the accelerator pedal and/or the speed of the vehicle.In addition, this device also includes a clutch torque control circuitwhich controls the clutch torque as a function of the difference betweena setpoint value, which is dependent on the position of the acceleratorpedal, and a return torque actual value, which is derived from theengine torque. This device facilitates comfortable driving off and/orgear changing by setting a clutch torque to a predefined value inaddition to the control of the engine rotational speed. As a resultchanges in torque during the clutch engagement process can be avoided.However, this document does not address the issues of the fuelconsumption or the emissions, nor does it provide for optimizationthereof.

One object of the present invention is to reduce consumption of fuel andthe emissions of pollutants during driving off processes in motorizedmotor vehicles.

This and other objects and advantages are achieved by the control methodaccording to the invention, in which, it is initially determined, bysensing the operational state and driving state of the vehicle, whethera driving off process is being carried out at a particular time. If so,in order to support the driver during the driving off process, theengine setpoint rotational speed is increased automatically andindependently of the driver, to a value which exceeds the idlingsetpoint rotational speed of the engine. The setpoint rotational speed,which is increased in comparison with the idling rotational speed, isfed as a setpoint value to a rotational speed controller, which in turnadjusts the engine actual rotational speed to the setpoint rotationalspeed by additional injection of fuel.

This technique provides the advantage that, irrespective of actuation ofthe accelerator pedal by the driver, the engine rotational speed isincreased to an optimum value which, under the given external conditionssuch as load pressure and atmospheric pressure, permits jolt-freedriving off, with minimum fuel consumption and minimum emissions ofpollutants. In this manner, the invention provides a saving potential ofapproximately 2 %, particularly when travelling in the city cycle.

These advantages come into effect in particular in small-volume internalcombustion engines which, due to their design, generate only arelatively small engine torque. With such engines, driving off requiresa comparatively high rotational speed which must be generated by thedriver by activating the accelerator pedal. Without the describeddriving off aid or the driving off assistant, however, the drivergenerally predefines an excessively high rotational speed in order toprevent the engine from stalling. The driving off assistant according tothe invention avoids unnecessarily high engine rotational speeds duringdriving off, so that the aforesaid saving potential is obtained.

In one preferred embodiment according to the invention the setpointrotational speed for the driving off process depends on the speed of thevehicle, and increases as the speed of the vehicle increases. However,it may be expedient to allow the setpoint rotational speed to increasedegressively as a function of the speed of the vehicle. This means thatthe speed of the vehicle also increases without actuation by the driver,with the increase becoming smaller and smaller as the speed increases.As a result, excessively high automatic increases in speed are avoided.

The rotational speed controller automatically converts the increasingengine speed into a corresponding actual rotational speed. Additionalhardware components are not required; and it is sufficient to set therotational speed controller correspondingly at the software level andsupply it with the setpoint rotational speed which supports the driver.

The method according to the invention is particularly suitable for usein vehicles with a manual transmission and a clutch, in which it ispossible to use the state of the clutch as a triggering criterion forthe use of the driving off assistant. The state of a clutch is detectedfor this purpose, and the setpoint rotational speed is automaticallyincreased if the clutch is in the declutched state and at the same timethe brakes of the vehicle are not activated. From the presence of theseconditions it is possible to infer a driving off process with sufficientreliability.

The automatic increase in the rotational speed can also be used tocompensate driver implemented clutch actuations that deviate from anoptimum movement. For example when the clutch is engaged too quickly andthe clutch slip is therefore reduced too strongly and the enginerotational speed decreases suddenly, the driving off assistant cancompensate by rapidly increasing in the injection quantity, ifappropriate up to the limiting value for the injection quantity. On theother hand, if the clutch is opened too wide and the clutch slip iscorrespondingly very high, the current setpoint rotational speed can bereduced, so that undesired harmonics of the engine rotational speed canbe avoided.

In order to avoid a situation in which, immediately after the enginestarts with the clutch pedal fully depressed, the driving off assistantis switched on and sets an increased idling rotational speedunnecessarily, triggering of the brake assistant directly after theengine starts can be coupled to the additional condition that the brakesof the vehicle are activated by the driver and subsequently releasedagain or else the driver activates the accelerator pedal. Increasedidling rotational speeds after the start are avoided by means of thisfunction.

According to a further expedient embodiment of the invention, the clutchis declutched when the vehicle is already moving, it is possible, tofirst maintain the engine setpoint rotational speed or reduce it andonly subsequently increase it again, for example after a rotationalspeed-maintaining time has expired or when some other condition applies,for example after the clutch has been engaged again. This decelerationof the clutch signal causes the driving off assistant to be activatedwith a time delay. As a result, in particular in stop-and-go mode whenthere is frequent actuation of the clutch pedal, an undesired increasein the setpoint rotational speed is avoided; instead, the engine brakecan be used to brake the vehicle. The driving off assistant is notactivated again until after the time delay has expired, and the enginerotational speed is increased again.

In the control system according to the invention, which is suitable inparticular for carrying out the method, a sensing device is provided forgenerating actuation signals that represent the operational state anddriving state of the vehicle. Furthermore, the engine actual rotationalspeed is set to a predefined engine setpoint rotational speed by meansof a rotational speed controller. A driving off process which is to becarried out at a particular time is detected by means of the sensingdevice, and an actuation signal is generated for supporting the driverduring the driving off process. The actuation signal is fed to therotational speed controller in which the engine setpoint rotationalspeed is set automatically and independently of the driver to a valuewhich exceeds the idling setpoint rotational speed. The actualrotational speed is adjusted to this increased setpoint rotationalspeed.

As an alternative to using the method or the system according to theinvention in vehicles with a manual transmission and a driver actuatedclutch, it is also possible to use such method or system in vehicleswith manual transmission and an automatic clutch, or in vehicles withautomatic transmissions.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE is a schematic diagram of a control system in a drive deviceof a vehicle for supporting the driving off processes.

DETAILED DESCRIPTION OF THE DRAWINGS

Rotational speed increments ΔL_(p) and ΔL_(v) (which are added to thenormal engine idling setpoint rotational speed) are determined in blocks1 and 2 of the control system, as a function of the atmospheric pressurep_(A) and the current speed v_(act) of the vehicle, in order to be ableto take into account the influence of the atmospheric pressure and ofthe speed of the vehicle. The dependence on the atmospheric pressurep_(A) is determined in the first block 1, the rotational speed incrementΔL_(p) increasing as the atmospheric pressure p_(A) decreases. In thesecond block 2, the rotational speed increment ΔL_(v) (which isdependent on the speed v_(act) of the vehicle) is determined, andbecomes smaller as the speed increases; the increase in the rotationalspeed depends degressively on the speed of the vehicle.

The rotational speed increments ΔL_(p) and ΔL_(v), are added in block 3and fed to the block 4 which is embodied as a switch.

The method branch which is illustrated in blocks 5 to 12 represents theswitch-on conditions or the actuation of the automatic increase inrotational speed when the vehicle drives off. In a block 5, the state ofthe clutch is determined and fed to a block 6 which is embodied as aswitch and whose switched state is influenced based on a comparison ofthe actual speed v_(act) from a block 7 with a minimum speed v_(min)from a block 8, in a block 9 which is embodied as a comparator. If thecurrent vehicle actual speed v_(act) is higher than the minimum speedv_(min), which represents a lower threshold value, this means that thevehicle is moving. If so, the switch of the block 6 is moved from thestate which is shown by an unbroken line into the state which is shownby dashed lines. A further block 10 performs a time delay with arotational speed-maintaining time t_(Main). During the rotationalspeed-maintaining time t_(Main), the brake assistant is not activated.The system continues to the further block 11 only after the rotationalspeed-maintaining time t_(Main) has expired.

If the result of the comparison in the block 9—embodied as acomparator—of the actual speed v_(act) and a minimum speed v_(min) isthat the actual speed is below the minimum speed v_(min), the vehicle isconsidered to be stationary. In this case, no signal is generated inblock 9, and the switched state of the switch 6 remains in the stateillustrated by the unbroken line according to which the system advancesdirectly to block 11, bypassing the rotational speed-maintaining timet_(Main) of the block 10.

In addition, a brake signal, representing the state of the brakes, isfed to the block 11 from a block 12, and an actuation signal isgenerated in the block 11 only if both a clutch signal which indicatesthat the clutch is declutched is supplied from the switch 6 and a signalwhich indicates that the brakes are not activated is supplied from theblock 12. If these two conditions are fulfilled, an actuation signalwhich is fed to the switch 4 is generated in the block 11, and saidswitch is moved into a position which is shown by a dashed line in whichthe sum of the rotational speed increments ΔL_(p) and ΔL_(v) is made topass through the switch 4 and is fed to a further block 13. In the block13, an overall rotational speed increment ΔL which is composed of thesum of the individual rotational speed increments ΔL_(p) and ΔL_(v) isdegressively increased according to a predefined decrementation ramp asthe speed of the vehicle v_(act) increases, so that the increase in therotational speed increment becomes smaller and smaller as the speed ofthe vehicle increases.

Subsequently, in block 14, a lower limitation of the rotational speedincrement is performed. In block 15, the ultimate rotational speedincrement ΔL is fed to a rotational speed controller in the enginecontrol device and added there to the setpoint idling rotational speed.As a result, the engine setpoint rotational speed which is to be set ata particular time is obtained.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1-13. (canceled)
 14. A method for controlling operation of a motorizedvehicle during driving, off comprising: sensing an operational state anda driving state of the vehicle; detecting a driving off process which isto be carried out at a particular time, based on said sensed operationaland driving states; supporting a vehicle driver, during driving off byincreasing an engine setpoint rotational speed, automatically andindependently of the driver, to a value which exceeds an idling setpointrotational speed of the engine; and a rotational speed controlleradjusting engine actual rotational speed to the setpoint rotationalspeed, by additional injection of fuel.
 15. The method as claimed inclaim 14, wherein: increasing of the setpoint rotational speed dependson the speed of the vehicle; and the setpoint rotational speed isincreased as the speed of the vehicle increases.
 16. The method asclaimed in claim 15, wherein the setpoint rotational speed is increaseddegressively as the speed of the vehicle increases.
 17. The method asclaimed in claim 1, wherein: in vehicles with a clutch, the state of theclutch is detected; and the setpoint rotational speed is increased ifthe clutch is in the declutched state and the brakes of the vehicle arenot activated.
 18. The method as claimed in claim 14, wherein invehicles with a clutch, the setpoint rotational speed is increasedautomatically immediately after the engine starts, only if the brakes ofthe vehicle have been activated and released again.
 19. The method asclaimed in claim 14, wherein in vehicles with a clutch, the setpointrotational speed is increased automatically immediately after the enginestarts, only if the accelerator pedal has been activated.
 20. The methodas claimed in claim 14, wherein the engine setpoint rotational speed isincreased as the atmospheric pressure decreases.
 21. The method asclaimed in claim 14, further comprising: detecting that the vehicle isalready rolling after declutching has been carried out; and initiallymaintaining or decreasing and subsequently increasing the enginesetpoint rotational speed.
 22. The method as claimed in claim 21,wherein the engine setpoint rotational speed is increased after aspeed-maintaining time.
 23. The method as claimed in claim 21, whereinthe engine setpoint rotational speed is increased when the clutch isengaged again.
 24. Apparatus for controlling a drive device in amotorized vehicle during driving off of the vehicle, said apparatuscomprising: a sensing device for generating actuation signals thatrepresent an operational state and a driving state of the vehicle; arotational speed controller for setting engine actual rotational speedto a predefined engine setpoint rotational speed; means for detecting adriving off process which is to be carried out at a particular time, andfor feeding an actuation signal to the rotational speed controller inorder to support the driver during the driving off process; wherein saidrotational speed controller increases the engine setpoint rotationalspeed automatically and independently of the driver to a value whichexceeds an idling setpoint rotational speed of the engine, and adjuststhe engine actual rotational speed to the predefined setpoint rotationalspeed.
 25. The apparatus as claimed in claim 24, in a vehicle with amanual shift transmission and an automatic clutch.
 26. The apparatus asclaimed in claim 24, in a vehicle with automatic transmission.